This invention relates generally to the field of catalysis, and more particularly relates to electron donor compounds for use with Ziegler-Natta polymerization catalysts. The invention additionally relates to novel Ziegler-Natta catalyst systems that employ an unsaturated nitrogenous compound as an electron donor, to methods for manufacturing Ziegler-Natta catalyst systems containing such compounds, and to methods for polymerizing addition polymerizable monomers, e.g., olefins, using a Ziegler-Natta catalyst system that employs an unsaturated nitrogenous compound as an internal and/or external electron donor.
The extensive use of polymers in daily life is largely attributable to improvements in polymer manufacturing processes as well as improvements in polymer properties. For polyolefin production, the work of Karl Ziegler and Giulio Natta, in the early 1950s, has served as a starting point for numerous advances in the technology.
The basis of the Ziegler catalysts was a complex of a transition metal compound with an organometallic compound (see Ziegler et al., U.S. Pat. Nos. 3,903,017, 4,063,009 and 4,125,698). One of the most preferred examples was titanium tetrachloride combined with triethylaluminum in a hydrocarbon solution. Using the new catalyst, Ziegler produced long chain polyethylene molecules from ethylene at atmospheric pressure. The polymerization of other olefins was also possible using the Ziegler catalysts.
Polymers produced using the early Ziegler catalysts were typically amorphous. Amorphous polymers, such as amorphous polyethylene, have inadequate material properties for a number of applications. Although the Ziegler catalyst systems made it easier to produce linear polyolefins, the resulting polymers had many properties like those of the polymers produced using competing processes involving either thermal-high pressure processes or chromium oxide catalysts. See F. Albert Cotton and Geoffrey Wilkinson, xe2x80x9cAdvanced Inorganic Chemistry: A Comprehensive Text,xe2x80x9d 3rd ed., Wiley and Sons, Inc., 1972, pp. 794-795.
Giulio Natta et al., U.S. Pat. Nos. 3,197,452 and 3,957,743, developed improved Ziegler type catalysts that permitted the production of higher quality polyolefins with stereochemical control properties, i.e. stereospecificity. The Natta catalysts allowed production of long chain polyolefins that were crystalline rather than amorphous. Control of the polymer stereochemistry required a crystalline catalyst surface. See Brian L. Goodall, xe2x80x9cPolypropylene: Catalyst and Polymerization Aspects,xe2x80x9d in Polypropylene and Other Polyolefins, ed. Ser van der Ven (Amsterdam: Elsevier Science Publishers B.V., 1990), at pp. 1-25. The stereospecificity depended on the particular crystalline phase. Titanium halides were found to produce the highest catalytic activity. Favored compounds were titanium trichloride and titanium tetrachloride with titanium trichloride preferred; both compounds gave similar results when used to produce crystalline polypropylene. Crystalline polypropylene was also obtained using vanadium, chromium, zirconium, and molybdenum compounds. Aluminum alkyls other than triethylaluminum produced crystalline polymers as well.
Further efforts to improve the performance of Ziegler-Natta catalysts included the use of a catalyst support for the active components of the catalyst. For example, Mayr et al., U.S. Pat. No. 4,495,338, describe the use of magnesium or zinc halide support materials with Ziegler-Natta catalyst components. Treatment of the catalyst with an electron donor (and/or polymerization in the presence of an electron donor) has also been found to increase the activity and selectivity of Ziegler-Natta catalysts. Several varieties of compounds have been found to have suitable properties as electron donors. Electron donating compounds used to process the transition metal component of Ziegler-Natta catalysts are called xe2x80x9cinternalxe2x80x9d electron donors, while those added during or immediately prior to polymerization are termed xe2x80x9cexternalxe2x80x9d electron donors.
Bailly et al., EP 336,545, described a method for preparing high activity Ziegler-Natta catalysts supported on magnesium dichloride substrates. As part of the catalyst preparation process, the magnesium dichloride support was contacted with electron donor compounds (i.e., as xe2x80x9cinternalxe2x80x9d electron donors) prior to incorporating the titanium component. The specified electron donors had labile hydrogen; suitable donor compounds included water, alcohols, phenols, thiols, and hydrogen sulfide. An optional step was also suggested that included treatment with an ester of an aromatic acid. The esters were chosen from ethyl benzoate, methyl paratoluate, and dibutyl or diisobutyl phthalate.
Although internal electron donors improved the selectivity and activity of Ziegler-Natta catalysts to some extent, a significant amount of amorphous polymer was still produced. It was later found that including an additional catalyst preparation step could increase the crystalline yield. The solution was to use a first electron donor treatment for the titanium component as well as a second electron donor treatment for the aluminum compound processing step (see Goodall supra).
Giannini et al., U.S. Pat. No. 4,107,414, processed Ziegler-Natta catalyst components supported on magnesium dichloride substrates with both internal and external electron donor compounds. The resulting catalysts had high activity and increased stereospecificity. Some of the recommended internal electron donor compounds were veratrol, ethyl benzoate, acetone, dimethylmalonate, and tetrahydrofuryl methyl ether. Giannini et al. also found that the diamines and esters of oxygenated organic and inorganic acids were particularly suitable for improving the activity and stereospecificity of the catalysts. Suitable external electron donor compounds included esters of oxygenated organic and inorganic acids.
Albizzati et al., U.S. Pat. No. 4,522,930, also describe use of both internal and external electron donors in Ziegler-Natta catalyst systems. The proposed internal electron donor compounds were ethers, ketones, lactones, esters, and compounds containing nitrogen, phosphorous and/or sulfur atoms. The external electron donors were compounds that contained Sixe2x80x94OR, Sixe2x80x94OCOR, or Sixe2x80x94NR2 groups.
Further development work on Ziegler-Natta catalysts led to the discovery of diethers as electron donors; see, e.g., EP 728,741 (Morini et al.), EP 361,949 (Scordamaglia et al.), and EP 362,705 (Barbe et al.).
To improve the performance of diether electron donors for Ziegler-Natta catalysts, mixtures of diethers plus other electron donors have been used in preparation of the catalysts. For example, Iiskola et al., U.S. Pat. No. 5,869,418, describe an external electron donor containing a diether compound and an alkoxysilane. The two-component external donor mixtures were found to result in an increase in isotacticity and a broader molecular weight distribution for the polymeric product.
To further improve the performance of diether electron donors, Albizzati et al., U.S. Pat. No. 5,068,213, produced catalysts using modified diethers or polyethers as internal electron donors. The modification included adding at least one heteroatom (nitrogen, sulfur, phosphorus, silicon, non-ether oxygen, halogen) and/or double bond to the diether or polyether. The result of using the modified diethers was a Ziegler-Natta catalyst with high activity and stereospecificity without the need for external electron donors.
Although the diether-prepared Ziegler-Natta catalysts are being adopted extensively for commercialization, there is still a significant need to further improve the performance of Ziegler-Natta catalysts. Another reason for continued development of Ziegler-Natta catalysts is the continuing need to further increase polymer processability and decrease the cost of producing both catalysts and polymers.
Thus, the art provides Ziegler-Natta catalysts prepared using selected compounds or selected classes of compounds having electron donor properties that improve catalyst performance. However, prior catalyst systems and electron donor compositions, as described above, fail to meet all of the requirements for Ziegler-Natta catalysts. The existing Ziegler-Natta catalysts and electron donor compounds are still inadequate with respect to activity, stereospecificity, and control of polymer properties. From a cost and manufacturability standpoint, it is desirable to further improve the performance of electron donors for Ziegler-Natta catalysts.
Accordingly, there is a need in the art for higher performance Ziegler-Natta catalyst systems. The present invention is addressed to the aforementioned need in the art, and provides novel Ziegler Natta catalyst systems having numerous advantages relative to prior systems, in that they:
(1) allow for exceptional control over the structure and properties of the polymeric product, particularly with regard to molecular weight, tacticity, and relative reactivity ratio;
(2) are highly active polymerization catalysts;
(3) have enhanced stability;
(4) display optimal hydrogen sensitivity; and
(5 ) are quite versatile and can be used in conjunction with a variety of monomer types.
The invention thus represents a significant advance in the field of catalysis.
Accordingly, it is a primary object of the invention to provide novel catalyst systems useful for the polymerization of addition polymerizable monomers, e.g., olefinic monomers.
It is another object of the invention to provide such catalyst systems which comprise a Ziegler-Natta catalyst in combination with an unsaturated nitrogenous compound as an electron donor.
It is an additional object of the invention to provide processes for preparing catalyst systems as described and claimed herein.
It is a further object of the invention to provide a method for preparing polyolefins or other polymers deriving from the polymerization of addition polymerizable monomers containing one or more degrees of unsaturation, using a Ziegler-Natta catalyst and an unsaturated nitrogenous compound as described herein as an internal electron donor.
It is yet a further object of the invention to provide a method for preparing polyolefins or other polymers deriving from the polymerization of addition polymerizable monomers containing one or more degrees of unsaturation, using a Ziegler-Natta catalyst and an unsaturated nitrogenous compound as described herein as an external electron donor.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In one aspect of the invention, then, a novel catalyst system is provided comprised of a supported Ziegler-Natta catalyst and an unsaturated nitrogenous compound as an electron donor. The unsaturated nitrogenous compound has the structural formula (I)
Axe2x80x94(L)mxe2x80x94Axe2x80x2xe2x80x83xe2x80x83(I)
wherein A is a first coordinating segment containing a coordinating nitrogen atom within a Cxe2x95x90N group, L is a substituted or unsubstituted lower hydrocarbylene linking group, m is zero or 1, and Axe2x80x2 is a second coordinating segment containing a second coordinating atom selected from the group consisting of N, O, S and P. When the second coordinating atom is N, it may or may not be contained within a Cxe2x95x90N group. Each Cxe2x95x90N group may be a true imine functionality contained within an acyclic molecular segment, or may represent a linkage within a heterocycle such as a pyridine or pyrimidine ring. Exemplary compounds encompassed by the structure of formula (I) include those having structure (II) 
wherein:
m and n are independently zero or 1;
q is an optional double bond;
X is N, O, S or P, with the provisos that (a) when X is N or P, then either n is 1 or q is present as a double bond, but not both, and (b) when X is O or S, then n is zero and q is absent;
R1, R6, and R7 are independently hydrido, hydrocarbyl or substituted hydrocarbyl, and R2 and R5 are independently hydrido, halo, hydrocarbyl or substituted hydrocarbyl, or R1 and R2 and/or R5 and R6 may be taken together to form a linkage xe2x80x94Qxe2x80x94, resulting in a five- or six-membered ring, wherein Q is xe2x80x94[(CR)a(Z)b]xe2x80x94 in which a is 2, 3 or 4, Z is N, O or S, b is zero or 1, the sum of a and b is 3 or 4, and R is selected from the group consisting of hydrido, halo, hydrocarbyl, hydrocarbyloxy, trialkylsilyl, NR82, OR9, and NO2, wherein R8 and R9 are each independently hydrocarbyl, or wherein R moieties on adjacent carbon atoms may be linked to form an additional five- or six-membered ring, or R2 and R5 may together form a linkage xe2x80x94Qxe2x80x94 as just defined; and
R3 and R4 are independently selected from the group consisting of hydrido and hydrocarbyl.
One subset of such unsaturated nitrogenous compounds useful as electron donors herein are bipyridyl compounds having the structure of formula (III) 
In formula (III), i and j are independently zero, 1, 2 or 3, and R10, R11, R12 and R13 are independently hydrido, hydrocarbyl or substituted hydrocarbyl, as defined for R1.
In another aspect of the invention, a novel method is provided for preparing a catalyst system comprised of a Ziegler-Natta catalyst and an unsaturated nitrogenous compound as an internal electron donor, wherein the method involves admixing the electron donor with the Ziegler-Natta catalyst or components thereof during manufacture of the catalyst system.
In a further aspect of the invention, a novel method is provided for catalyzing polymerization of addition polymerizable monomers such as olefins, wherein the method involves contacting the addition polymerizable monomers, under polymerization conditions, with (1) a Ziegler-Natta catalyst system containing or prepared with an unsaturated nitrogenous compound as an internal electron donor, and/or (2) a Ziegler-Natta catalyst and, separately, an unsaturated nitrogenous compound as an external electron donor.
Definitions and Nomenclature
Before the present compounds, compositions and methods are disclosed and described, it is to be understood that unless otherwise indicated this invention is not limited to specific molecular structures, ligands, or the like, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
It must be noted that, as used in the specification and the appended claims, the singular forms xe2x80x9ca,xe2x80x9d xe2x80x9canxe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to xe2x80x9can electron donorxe2x80x9d includes one or more electron donors, reference to xe2x80x9ca monomerxe2x80x9d includes mixtures of different monomers, and the like.
The term xe2x80x9celectron donorxe2x80x9d or xe2x80x9celectron-donating compoundxe2x80x9d refers to a compound that donates a pair of electrons, e.g., to an organometallic compound or complex used as a polymerization catalyst. Electron donors can be used in two ways in the formation of a Ziegler-Natta catalyst system and use thereof. An xe2x80x9cinternalxe2x80x9d electron donor is used in the formation of the catalyst, while an xe2x80x9cexternalxe2x80x9d electron donor (also termed a xe2x80x9cselectivity control agentxe2x80x9d) is used in the polymerization reaction. The electron donors herein may be used as internal donors, external donors, or both.
The term xe2x80x9calkylxe2x80x9d as used herein refers to a branched or unbranched saturated hydrocarbon group of 1 to approximately 24 carbon atoms, typically 1 to approximately 12 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl and the like, as well as cycloalkyl groups such as cyclopentyl, cyclohexyl and the like. The term xe2x80x9clower alkylxe2x80x9d intends an alkyl group of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.
The term xe2x80x9calkenylxe2x80x9d as used herein refers to a branched or unbranched hydrocarbon group of 2 to approximately 24 carbon atoms, typically 2 to approximately 12 carbon atoms, containing at least one carbon-carbon double bond, such as ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, t-butenyl, octenyl, decenyl, tetradecenyl, hexadecenyl, eicosenyl, tetracosenyl and the like. Preferred alkenyl groups herein contain 2 to 12 carbon atoms and 2 to 3 carbon-carbon double bonds. The term xe2x80x9clower alkenylxe2x80x9d intends an alkenyl group of 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, containing one xe2x80x94Cxe2x95x90Cxe2x80x94 bond. The term xe2x80x9ccycloalkenylxe2x80x9d intends a cyclic alkenyl group of 3 to 8, preferably 5 or 6, carbon atoms.
The term xe2x80x9calkynylxe2x80x9d as used herein refers to a branched or unbranched hydrocarbon group of 2 to approximately 24 carbon atoms, typically 2 to approximately 12 carbon atoms, containing at least one xe2x80x94Cxe2x89xa1Cxe2x80x94 bond, such as ethynyl, n-propynyl, isopropynyl, n-butynyl, isobutynyl, t-butynyl, octynyl, decynyl and the like. The term xe2x80x9clower alkynylxe2x80x9d intends an alkynyl group of 2 to 6, preferably 2 to 4, carbon atoms, and one xe2x80x94Cxe2x89xa1Cxe2x80x94 bond.
The term xe2x80x9calkoxyxe2x80x9d as used herein intends an alkyl group bound through a single, terminal ether linkage; that is, an xe2x80x9calkoxyxe2x80x9d group may be defined as xe2x80x94OR where R is alkyl as defined above. A xe2x80x9clower alkoxyxe2x80x9d group intends an alkoxy group containing 1 to 6, more preferably 1 to 4, carbon atoms. Similarly, the term xe2x80x9calkenyloxyxe2x80x9d as used herein intends an alkenyl group bound through a single, terminal ether linkage, and xe2x80x9calkynyloxyxe2x80x9d refers to an alkynyl group bound through a single, terminal ether linkage.
The term xe2x80x9carylxe2x80x9d as used herein refers to an aromatic species containing 1 to 5 aromatic rings, either fused or linked, and either unsubstituted or substituted with 1 or more substituents typically selected from the group consisting of xe2x80x94(CH2)xxe2x80x94NH2, xe2x80x94(CH2)xxe2x80x94COOH, xe2x80x94NO2, halogen, alkyl, alkenyl, alkynyl, alkoxy, alkenyloxy, alkynyloxy, alkylthio, aryl, aralkyl, and the like, where x is an integer in the range of 0 to 6 inclusive as outlined above. Preferred aryl substituents contain 1 to 3 fused aromatic rings, and particularly preferred aryl substituents contain 1 aromatic ring or 2 fused aromatic rings. The terms xe2x80x9caralkylxe2x80x9d and xe2x80x9calkarylxe2x80x9d refer to moieties containing both alkyl and aryl species, typically containing less than about 24 carbon atoms, and more typically less than about 12 carbon atoms in the alkyl segment of the moiety, and typically containing 1 to 5 aromatic rings. The term xe2x80x9caralkylxe2x80x9d refers to aryl-substituted alkyl groups, while the term xe2x80x9calkarylxe2x80x9d refers to alkyl-substituted aryl groups. The terms xe2x80x9caralkylenexe2x80x9d and xe2x80x9calkarylenexe2x80x9d are used in a similar manner to refer to aryl-substituted alkylene and alkyl-substituted arylene moieties.
The term xe2x80x9cheterocyclicxe2x80x9d refers to a five- or six-membered monocyclic structure or to an eight- to eleven-membered bicyclic structure which is either saturated or unsaturated. Each heterocycle consists of carbon atoms and from one to four heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur. As used herein, the terms xe2x80x9cnitrogen heteroatomsxe2x80x9d and xe2x80x9csulfur heteroatomsxe2x80x9d include any oxidized form of nitrogen and sulfur, and the quaternized form of any basic nitrogen. Examples of heterocyclic groups include piperidinyl, pyrazinyl, morpholinyl and pyrrolidinyl.
xe2x80x9cHaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d refers to fluoro, chloro, bromo or iodo, and usually relates to halo substitution for a hydrogen atom in an organic compound. Of the halos, chloro and fluoro are generally preferred.
xe2x80x9cHydrocarbylxe2x80x9d refers to univalent unsubstituted and substituted hydrocarbyl radicals containing 1 to about 24 carbon atoms, typically 1 to about 12 carbon atoms, including branched or unbranched, saturated or unsaturated species, such as alkyl groups, alkenyl groups, aryl groups, heteroaryl groups, and the like. The term xe2x80x9clower hydrocarbylxe2x80x9d intends a hydrocarbyl group of one to six carbon atoms, preferably one to four carbon atoms. The term xe2x80x9chydrocarbylenexe2x80x9d intends a divalent unsubstituted or unsubstituted hydrocarbyl containing 1 to about 24 carbon atoms, including branched or unbranched, saturated or unsaturated species, or the like. The term xe2x80x9clower hydrocarbylenexe2x80x9d intends a hydrocarbylene group of one to six carbon atoms, preferably one to four carbon atoms. The term xe2x80x9chydrocarbyloxyxe2x80x9d or xe2x80x9chydrocarbylthioxe2x80x9d refer to a hydrocarbyl group bound through a terminal ether or thio linkage.
By xe2x80x9csubstitutedxe2x80x9d as in xe2x80x9csubstituted hydrocarbylxe2x80x9d or xe2x80x9csubstituted hydrocarbylenexe2x80x9d is meant that the hydrocarbyl or hydrocarbylene group contains one or more substituent groups which are inert under the process conditions to which the compound containing these groups is subjected. The substituent group may replace a hydrogen atom or may be found as a linkage within the carbon chain. xe2x80x9cMonosubstitutedxe2x80x9d refers to a hydrocarbyl or hydrocarbylene group having one substituent group and xe2x80x9cdisubstitutedxe2x80x9d refers to a hydrocarbyl or hydrocarbylene group containing two substituted groups. The substituent groups also do not substantially interfere with the process. Included in the meaning of xe2x80x9csubstitutedxe2x80x9d are heteroaromatic rings. Examples of substituents include, but are not limited to, amino (including primary amino and alkyl-substituted, typically lower alkyl-substituted, secondary and tertiary amino), alkyl (typically lower alkyl), alkoxy (typically lower alkoxy), alkenyl (typically lower alkenyl), aryl (e.g., phenyl), halo, haloalkyl, imino, nitro, and the like; xe2x80x9csubstitutedxe2x80x9d also refers to the replacement of a carbon atom in a hydrocarbyl or hydrocarbylene group with a non-hydrocarbyl linkage such as xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94N(alkyl)-, etc.
The term xe2x80x9cunsaturated nitrogenous compoundxe2x80x9d refers to a compound having a Cxe2x95x90N moiety. Unsaturated nitrogenous compounds herein include both a true imine wherein the Cxe2x95x90N moiety is present in an acyclic molecular segment, as well as nitrogenous heterocycles in which the carbon-nitrogen bond is present in an aromatic ring, e.g., as in pyridine, pyrimidine, pyrazine, and the like.
The term xe2x80x9cstereoregularityxe2x80x9d is used in the conventional sense to refer to the relative positioning of substituent groups of monomer units in a polymer chain. The term xe2x80x9cstereostructurexe2x80x9d refers to the stereoregularity of any particular polymer. Possible polymeric stereostructures include the following: atactic polymers, in which the arrangement of substituents is random; isotactic polymers, in which all substituents are identically oriented; syndiotactic polymers, in which the orientation of substituents alternates; stereoblock polymers, containing blocks of monomers all oriented the same way, and blocks of monomers all oriented in a different way; isoblock polymers, containing blocks of isotactic monomer units separated by a single oppositely oriented monomer unit; hemiisotactic polymers, having every other monomer unit oriented in the same way (isotactic), separated by a monomer that is randomly oriented; and hemisyndiotactic polymers having every other monomer unit oriented in the opposite way (syndiotactic), separated by a randomly oriented monomer unit. Use of the electron donors provided herein significantly reduces the amount of atactic material in the polymer product.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase xe2x80x9coptionally substituted hydrocarbylxe2x80x9d means that a hydrocarbyl moiety may or may not be substituted and that the description includes both unsubstituted hydrocarbyl and hydrocarbyl where there is substitution.
As used herein all reference to the Periodic Table of the Elements and groups thereof is to the version of the table published by the Handbook of Chemistry and Physics, CRC Press, 1995, which uses the IUPAC system for naming groups.
The Novel Catalyst System
In one embodiment, the invention provides a novel catalyst system in the form of a supported Ziegler-Natta catalyst comprised of a transition metal component and an organoaluminum cocatalyst in association with an unsaturated nitrogenous compound as an electron donor. The unsaturated nitrogenous compound has the structure of formula (I)
Axe2x80x94(L)mxe2x80x94Axe2x80x2xe2x80x83xe2x80x83(I)
wherein m is zero or 1, and A, L and Axe2x80x2 are defined as follows.
The molecular segment xe2x80x9cAxe2x80x9d represents an unsaturated nitrogenous moiety. More particularly, A is a first coordinating segment containing a coordinating nitrogen atom within a Cxe2x95x90N group. The Cxe2x95x90N group may be a true imine functionality contained within an acyclic molecular segment, or it may represent a linkage within a heterocycle such as a pyridine or pyrimidine ring. Preferred A moieties have the structures 
wherein R1 is hydrido, unsubstituted hydrocarbyl or substituted hydrocarbyl, including but not limited to, linear, branched or cyclic alkyl, alkenyl or alkynyl, aryl, alkaryl, aralkyl, heteroaryl, optionally substituted at one or more available carbon atoms with a nonhydrogen substituent such as halo, haloalkyl, alkoxy, hydroxyl, carboxyl, amino, mono(alkyl)substituted amino, di(alkyl)substituted amino, imino, nitro, trialkylsilyl, etc., and optionally containing one or more nonhydrocarbyl linkages such as xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94N(alkyl)- and the like. When R1 is other than hydrido, it will generally comprise 1 to 24 carbon atoms, more typically 1 to 12 carbon atoms; further, when R1 does not comprise a cyclic alkyl, aryl or heterocyclic substituent, it is preferably lower hydrocarbyl such as lower alkyl, lower alkenyl, or the like. R2, R2a and R2b are hydrido, halo or optionally substituted hydrocarbyl, with suitable hydrocarbyl moieties as defined for R1, and wherein R2a and R2b may be linked to form five- or six-membered alicyclic ring optionally containing 1, 2 or 3 heteroatoms, e.g., N, S, O or P, generally N or O. R1 and R2 may also be linked through a linkage xe2x80x94Qxe2x80x94, resulting in a five- or six-membered ring, wherein Q is xe2x80x94[(CR)a(Z)b]xe2x80x94 in which a is 2, 3 or 4, Z is N, O or S, b is zero or 1, the sum of a and b is 3 or 4, and R is selected from the group consisting of hydrido, halo, hydrocarbyl, hydrocarbyloxy, trialkylsilyl, NR82, OR9, and NO2, wherein R8 or R9 are each independently hydrocarbyl, or wherein R moieties on adjacent carbon atoms may be linked to form an additional five- or six-membered ring.
Axe2x80x2 is a second coordinating segment containing a second coordinating atom selected from the group consisting of N, O, S and P. If the second coordinating atom is N, it may or may not be contained in a Nxe2x95x90N group. Axe2x80x2 may be comprise virtually any molecular moiety which provides the aforementioned second coordinating atom within an optimum distance from the first coordinating atom in segment A; the xe2x80x9coptimum distancexe2x80x9d is such that one, two or three atoms may be present in a linear linkage between the first coordinating atom of segment A and the second coordinating atom of segment Axe2x80x2. Axe2x80x2 may be, for example, xe2x80x94OH, xe2x80x94SH, xe2x80x94COOH, xe2x80x94OR14, xe2x80x94SR14, xe2x80x94COOR14, 
wherein R14 is lower alkyl, and wherein any of the foregoing cyclic moieties may be substituted at an available carbon atom with a nonhydrogen substituent; 
wherein n is zero or 1, q is a single or double bond, X is N, O, S or P, R5 is as defined for R2, and R6 and R7 are as defined for R1, with the proviso that (a) when X is N or P, then either n is 1 or q is a double bond, but not both, and (b) when X is O or S, then n is zero and q is a single bond, and wherein R5 and R6 may be linked to form xe2x80x94Qxe2x80x94 as explained with respect to the possible linkage of R1 and R2 in molecular segment A; or 
wherein s and t are independently zero or 1, q, X, R2a, R2b and R6 are as defined above, and R2c is as defined for R2a and R2b, with the proviso that (a) when X is N or P, then either s is zero or q is a double bond, (b) when X is O or S, then s is zero and q is a single bond, and (c) when q is a double bond, t is zero; while when q is a single bond, then t is 1.
L is hydrocarbylene, preferably lower hydrocarbylene, either substituted or unsubstituted, and most preferably is substituted or unsubstituted methylene xe2x80x94CR3R4xe2x80x94 wherein R3 and R4 are hydrido or hydrocarbyl, preferably hydrido or alkyl, and most preferably hydrido or lower alkyl.
Exemplary unsaturated nitrogenous compounds useful as electron donors herein have the structure of formula (II) 
In formula (II), the subscripts m and n are independently zero or 1, preferably are both zero, and letter xe2x80x9cqxe2x80x9d represents an optional double bond.
X is N, O, S or P, with the provisos that (a) when X is N or P, then either n is 1 or q is present as a double bond, but not both, and (b) when X is O or S, then n is zero and q is absent.
R1, R6 and R7 are independently hydrido, hydrocarbyl or substituted hydrocarbyl, as defined above, and R2 and R5 are independently hydrido, halo, hydrocarbyl or substituted hydrocarbyl, also as defined above, or R1 and R2 and/or R5 and R6 may be taken together to form a linkage xe2x80x94Qxe2x80x94, resulting in a five- or six-membered cyclic group. Similarly, R2 and R5 may together form a linkage xe2x80x94Qxe2x80x94. As explained above, Q is xe2x80x94[(CR)a(Z)b]xe2x80x94 in which a is 2, 3 or 4, Z is N, O or S, b is zero or 1, the sum of a and b is 3 or 4, and R is selected from the group consisting of hydrido, halo, hydrocarbyl, hydrocarbyloxy, trialkylsilyl, NR82, OR9, and NO2, wherein R8 or R9 are each independently hydrocarbyl, or wherein R moieties on adjacent carbon atoms may be linked to form an additional five- or six-membered ring.
Examples of R1, R6 and R7 thus include, but are not limited to, hydrido, methyl, ethyl, n-propyl, isopropyl, methoxy, ethoxy, isopropoxy, phenyl, benzyl, phenoxy, pyridyl, diisopropylphenyl, methoxyphenyl, trimethylsilyl, triethylsilyl, and the like; R2 and R5 substituents can include any of the foregoing as well as halogen substituents, i.e., chloro, fluoro, bromo and iodo, with chloro and fluoro preferred. When R1 and R2 and/or R5 and R6 are linked, the cyclic structures so formed may be alicyclic or aromatic, including, for example, furanyl, pyrrolyl, thiophenyl, imidazolyl, pyrazolyl, oxathiolyl, pyridinyl, methylpyridinyl, ethylpyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, piperidinyl, piperazinyl, morpholinyl, tetrahydrothiophenyl, tetrahydrofuranyl, tetrahydropyranyl, 1,4-dioxanyl, etc. When R2 and R5 are linked, the resulting structures are alicyclic and may or may not contain heteroatoms; such moieties include, for example, cyclopentane, cyclohexane, tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, 1,4-dioxane, 1,2-dithiole, 1,3-dithiole, piperazine, morpholine, and the like.
R3 and R4 are independently selected from the group consisting of hydrido and hydrocarbyl, preferably hydrido or alkyl, most preferably hydrido or lower alkyl.
In one group of compounds having the general structure of formula (II), m and n are zero, X is N, and q represents a double bond, so that the compound has the structure (IV) 
in which R1, R2, R5 and R6 are as defined previously.
Another group of compounds having the structure of formula (II) (and encompassed by formula (IV) as well) are bipyridyl compounds having the structure of formula (III) 
Exemplary compounds within this group are wherein i and j are zero and R10 and R11 are lower alkyl, i.e., 3,3xe2x80x2-di(lower alkyl)-2,2xe2x80x2-bipyridine, including, for example, 3,3xe2x80x2-dimethyl-2,2xe2x80x2-bipyridine.
In another group of compounds encompassed by structural formula (II), m and n are zero, X is O, and q is absent, such that the compound has the structure of formula (V) 
wherein R1, R2, R5 and R6 are as defined previously, particularly with respect to compounds of formula (IV).
Specific electron donors herein include, but are not limited to, the following: 
When used as an internal electron donor, an unsaturated nitrogenous compound as defined above is combined with, or used in the preparation of, a Ziegler-Natta catalyst system prior to its use in polymerization. The electron donors herein may be used in conjunction with virtually any type of Ziegler-Natta catalyst, catalyst components or catalyst systems, as will be appreciated by those skilled in the art. Typically, however, the Ziegler-Natta catalyst is supported on a base selected from the group consisting of inorganic metal salts and oxides. The catalyst is comprised of two components: a transition metal component; and an aluminum-containing or boron-containing cocatalyst.
The transition metal component of the Ziegler-Natta catalyst generally has the formula M(R)x(ORxe2x80x2)y-x wherein M is a transition metal, typically a Group IVA, VA or VIA transition metal; R is halo, preferably although not necessarily chloro or bromo; Rxe2x80x2 is a substituted or unsubstituted hydrocarbyl group having from 1 to about 24, preferably from 1 to about 10 carbon atoms; y is the valence state of M, and x is an integer in the range of 0 to y. Preferably, x is less than y, so that at least one of the halo substituents is replaced with an ORxe2x80x2 moiety. Most preferably, although again, not necessarily, M is titanium, vanadium, zirconium, chromium or hafnium. Exemplary transition metal components thus include, without limitation, tetramethyl zirconium, tetramethyl titanium, tetrabenzyl titanium, tetrabenzyl zirconium, tetrakis (dimethyl amido) titanium, tetrakis (dimethyl amido) zirconium, vanadium trichloride, chromium trioxide and triallyl chromium, tetra-n-butoxy titanium, tetra(isopropoxy)titanium, tetraethoxy titanium, di-n-butoxy titanium dichloride, monoethoxy titanium trichloride, tetraphenoxy titanium, triethoxy titanium chloride, triisopropoxy titanium chloride, diethoxy titanium dibromide, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetraethoxy hafnium, tetraethoxy zirconium, triethoxy zirconium bromide, triisopropoxy hafnium chloride, di-n-butoxy zirconium dichloride, vanadium tetrachloride, vanadium tetrabromide, zirconium tetrachloride, zirconium tetrabromide, and the like. Mixtures of such components may also be used in a single catalyst system, as will be appreciated by those skilled in the art.
The cocatalyst, if aluminum-containing, will generally be an organoaluminum compound. Suitable organoaluminum cocatalysts include aluminum trialkyl compounds AlRxe2x80x33 wherein Rxe2x80x3 is C1-C12 alkyl, such as, for example, triethylaluminum, trimethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum and the like. Other organoaluminum cocatalysts are aluminoxanes Al(O)R2 wherein R is an alkyl group having from 1 to about 8 carbon atoms and x has a value greater than about 5, e.g., methylaluminoxane (xe2x80x9cMAOxe2x80x9d), hexaisobutyl aluminoxane, tetraisobutyl aluminoxane and polymethylaluminoxane. Other suitable organoaluminum compounds may serve as cocatalysts as well, however, including alkyl aluminum halides such as diethylaluminum chloride, diethylaluminum bromide, methylethylaluminum chloride, etc.; alkyl aluminum hydrides; and alkyl siloxalanes. If boron-containing, the cocatalyst will typically be a fluorohydrocarbylboron compound such as tetra(pentafluorophenyl)borate, sodium tetrakis[(bis-3,5-trifluoromethyl)phenyl]borate, H+(OCH2CH3)2[(bis-3,5-trifluoromethyl)phenyl]borate, trityltetra(pentafluorophenyl)borate or tris(pentafluorophenyl)boron. The relative amounts of cocatalyst and transition metal component that are used are such that the atomic ratio of Al (or B) to M (e.g., Zr, Hf, etc.) is from about 0.1:1 to about 2000:1, preferably from about 1:1 to about 1000:1, more preferably from about 5:1 to about 500:1, and most preferably from about 5:1 to about 200:1.
The Ziegler-Natta catalyst is supported on a base generally selected from the group consisting of inorganic metal oxides and salts, e.g., silica, magnesium salts and oxides, manganese salts and oxides. Combinations of such compounds may also be used. Magnesium and manganese salts and oxides are preferably employed, alone or in combination with other compounds, e.g., silica, aluminum salts, or the like. Particularly preferred magnesium and manganese salts and oxides include, for example, magnesium and manganese dihalides, alkyl oxides, aryl oxides and combinations thereof. Particularly preferred support bases are the magnesium dialkoxides, halo magnesium alkoxides and magnesium dihalides. Illustrative but nonlimiting examples of suitable support bases include MgCl2, MgCl2/AlCl3, MgCl2/SiO2,MgBr2, Mg(OCH3)2, Mg(OCH2CH3)2, Mg(OC6H5)2 and combinations thereof. In accordance with the preferred embodiments of this invention, the magnesium halides and especially magnesium dichloride are used to form the support material. The solid support is particulate in nature, and preferably has a median particle diameter from about 0.1 xcexcm to about 500 xcexcm, more preferably from about 1 xcexcm to about 150 xcexcm, and most preferably from about 5 xcexcm to about 100 xcexcm. The amount of support material in the catalyst system is such that an atomic ratio of Mg or Mn in the support, to Al (or B) in the cocatalyst, is greater than 0.3 to 1, and preferably is in the range of approximately 0.5:1 to 10:1.
The preferred method for producing the catalyst system of the invention in this embodiment, i.e., wherein the unsaturated nitrogenous compound serves as an xe2x80x9cinternalxe2x80x9d electron donor, comprises comminution of all components, i.e., the transition metal component, the aluminum-containing or boron-containing cocatalyst, the support material, and the electron donor. This may be accomplished using any methodology and equipment known and available to those skilled in the art. Generally, admixture and comminution of the ingredients is carried out under an inert atmosphere in a ball or vibration mill. Initially, it is preferred that the support base is charged into the mill; if the support base material contains water which must be removed, a sufficient quantity of dehydrating agent is initially added to the support base. Although comminution may take place at temperatures between about 0xc2x0 C. and about 90xc2x0 C., the preferred mixing temperature is from about 25xc2x0 C. to about 50xc2x0 C. Mixing times may range from about 15 minutes to about 48 hours. Preferred mixing times are from about 12 hours to about 20 hours, optimally about 16 hours.
Another suitable technique is a precipitation method that typically involves: (1) admixing R2Mg (R=alkyl, alkoxide, carboxylate) with MCl4 (M=transition metal) in a hydrocarbon solvent to precipitate the solid catalyst intermediate, and (2) treating the intermediate so formed with a second transition metal compound (often TiCl4 or TiMe4) and an electron donor to form the catalyst system. The catalyst system is then activated using a typical catalyst activator, e.g., an aluminum alkyl or MAO. As will be appreciated by those skilled in the art, there are a number of variables that may be optimized using routine procedures to produce a desired catalyst system, including method/order of addition, stirring speed, mixing temperature (typically 25xc2x0 C.-130xc2x0 C.), and the like; optimal conditions depend on the reagents used.
The present invention is thus premised in part on the discovery that using an unsaturated nitrogenous compound as an internal electron donor in a Ziegler-Natta catalyst system, particularly a monoimine, a diimine or a bipyridyl compound, significantly improves catalyst efficiency and reduces formation of atactic product. That is, catalyst efficiency is substantially higher than that seen with prior Ziegler-Natta catalyst systems, with or without electron donors that have been used previously, including esters, ethers, ketones, lactones, alkoxysilanes, and the like. Furthermore, the properties of the polymer product are far superior, as a result of the increase in stereoregularity. Stereoregular polymers typically have high crystallinity, which is in turn a prime determinant of key physical properties such as stiffness, solvent resistance, and melting temperature. The fact that the present catalyst systems are highly efficient and prepare polymers having high stereoregularity is a significant advantage of the invention.
External Electron Donors
In an alternative embodiment of the invention, unsaturated nitrogenous compounds as described earlier herein are used as external electron donors. That is, they are incorporated into a polymerization reaction either during polymerization or immediately prior to polymerization. The catalyst system that is used is a Ziegler-Natta catalyst system described in the preceding section, i.e., a catalyst system comprised of a supported Ziegler-Natta catalyst having a transition metal component and an aluminum-containing or boron-containing cocatalyst. In this embodiment, however, the unsaturated nitrogenous compound may not be present in the initial catalyst system, and thus represents an xe2x80x9cexternalxe2x80x9d electron donor.
Polymerization
In another embodiment of the invention, a process is provided for polymerizing addition polymerizable monomers using either (1) a catalyst system as described herein containing an unsaturated nitrogenous compound as an internal electron donor, and/or (2)an unsaturated nitrogenous compound as an external electron donor. The addition polymerizable monomers contain one or more degrees of unsaturation. Olefinic or vinyl monomers are preferred, and particularly preferred monomers are xcex1-olefins having from about 2 to about 20 carbon atoms, such as, for example, linear or branched olefins including ethylene, propylene, 1-butene, 3-methyl-1-butene, 1,3-butadiene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1,4-hexadiene, 1,5-hexadiene, 1-octene, 1,6-octadiene, 1-nonene, 1-decene, 1,4-dodecadiene, 1-hexadecene, 1-octadecene, and mixtures thereof. Cyclic olefins and diolefins may also be used; such compounds include, for example, cyclopentene, 3-vinylcyclohexene, norbornene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, dicyclopentadiene, 4-vinylbenzocyclobutane, tetracyclododecene, dimethano-octahydronaphthalene, and 7-octenyl-9-borabicyclo-(3,3,1)nonane. Aromatic monomers which may be polymerized include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-tert-butylstyrene, m-chlorostyrene, p-chlorostyrene, p-fluorostyrene, indene, 4-vinylbiphenyl, acenaphthalene, vinylfluorene, vinylanthracene, vinylphenanthrene, vinylpyrene and vinylchrisene. Other monomers which may be polymerized include methylmethacrylate, ethylacrylate, vinyl silane, phenyl silane, trimethylallyl silane, acrylonitrile, maleimide, vinyl chloride, vinylidene chloride, tetrafluoroethylene, isobutylene, carbon monoxide, acrylic acid, 2-ethylhexylacrylate, methacrylonitrile and methacrylic acid.
In order to carry out the polymerization reaction, a catalytic amount of a catalyst system of the invention, containing an unsaturated nitrogenous compound as an internal electron donor, is brought into contact with the addition polymerizable monomers contained in a polymerization zone. Alternatively, a catalyst system is used which does not contain an internal electron donor, but wherein an unsaturated nitrogenous compound is added into the polymerization reaction as an external electron donor. In a further embodiment, an unsaturated nitrogenous compound is used as both an internal electron donor and an external electron donor in a single polymerization process. In any of the foregoing embodiments, polymerization may be carried out in the liquid or slurry phase, in which case reaction is carried out in the presence of an inert diluent, i.e., an inert organic diluent such as liquefied ethane, propane, isobutane, n-butane, n-hexane, isooctane, paraffinic mixtures of alkanes having from 8 to 12 carbon atoms, cyclohexane, methylcyclopentane, dimethylcyclohexane, dodecane, benzene, toluene, ethylbenzene, cumene, decalin, kerosene, naphthas, etc. Preferred polymerization temperatures are from about 60xc2x0 C. to about 95xc2x0 C., and preferred pressures generally range from 10 to 2000 atm. Polymerization may also take place in the gas phase, e.g., in a fluidized or stirred bed reactor, using temperatures in the range of approximately 60xc2x0 C. to 120xc2x0 C. and pressures in the range of approximately 10 to 1000 atm.
It is to be understood that while the invention has been described in conjunction with the preferred specific embodiments thereof, that the foregoing description as well as the examples which follow are intended to illustrate and not limit the scope of the invention. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.
All patents, patent applications, and publications mentioned herein are hereby incorporated by reference in their entireties.
Experimental
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to prepare and use the catalysts of the invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in xc2x0C. and pressure is at or near atmospheric.